Adhesive tape, laminate, and electronic apparatus

Abstract

The purpose of the present invention is to provide an adhesive tape which is capable of exhibiting excellent adhesive force to a silicone-based adherend. An adhesive tape according to the present invention has an adhesive layer that contains a (meth)acrylic copolymer. A laminate which is obtained by bonding the adhesive tape to a silicone rubber that is affixed to an SUS304 plate is left to stand for 72 hours in an environment at 25°C and 50% RH, and is subsequently subjected to a peel test in which the adhesive tape in the laminate is peeled at 180° from the silicone rubber under conditions of 23°C, 50% RH, and a peeling rate of 300 mm / min using a tensile tester. If the surface, from which the adhesive tape has been separated, of the silicone rubber after the peel test is cleaned at least eight times with ethyl acetate and is subsequently subjected to TOF-SIMS measurement, the peak intensity (26 / total) of negative ions in a region where m / z is 26 with respect to the peak intensity (total) of all negative ions is 2.50 × 10-3 or more.

Description

Adhesive tape, laminate, and electronic device

[0001] The present disclosure relates to a pressure-sensitive adhesive tape. The present disclosure also relates to a laminate having a structure to which the pressure-sensitive adhesive tape is attached, and an electronic device including the pressure-sensitive adhesive tape.

[0002] BACKGROUND ART Pressure-sensitive adhesive tapes are widely used in a variety of fields, for example, for assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), or for fixing in-vehicle electronic device components such as in-vehicle panels to vehicle bodies (e.g., Patent Documents 1 and 2).

[0003] JP 2009-242541 A JP 2009-258274 A

[0004] In recent years, in response to the trend toward PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds) regulations, there has been a movement to reduce the use of fluororesins in the assembly and fixation of electronic devices. Silicone materials are an example of an alternative to fluorine-based materials, which are characterized by low surface energy. When adhesive tapes with adhesive layers made of relatively high-surface-energy urethane-based adhesives, acrylic-based adhesives, hydrocarbon-based adhesives, etc. are used with silicone materials, which have low surface energy, the interfacial adhesive strength is insufficient. Therefore, when adhering silicone materials, adhesive tapes with adhesive layers made of silicone-based adhesives have typically been used.

[0005] However, in adhesive tapes that use a silicone-based adhesive as an adhesive layer, the current situation is that a separator that protects the adhesive layer must have a release layer containing a fluororesin to facilitate peeling from the silicone-based adhesive.

[0006] On the other hand, when using an adhesive tape having an adhesive layer made of an adhesive other than a silicone-based adhesive when adhering a silicone material, it is necessary to perform surface treatment such as corona treatment or primer treatment on the surface of the silicone material to be adhered, which poses problems from the viewpoints of reduced work efficiency, the need for additional equipment, etc. For these reasons, there has been a problem in that it is difficult to design an adhesive tape that does not contain a fluororesin and can firmly adhere a silicone material without prior surface treatment.

[0007] The present disclosure aims to provide a pressure-sensitive adhesive tape that can exhibit excellent adhesive strength to a silicone-based adherend without using a silicone-based pressure-sensitive adhesive and without prior surface treatment of the adherend. The present disclosure also aims to provide a laminate having a structure to which the pressure-sensitive adhesive tape is attached. A further object of the present disclosure is to provide an electronic device that includes the pressure-sensitive adhesive tape.

[0008] Disclosure 1 provides a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a (meth)acrylic copolymer, wherein a laminate obtained by laminating the pressure-sensitive adhesive tape to silicone rubber fixed to a SUS304 plate is left to stand for 72 hours in an environment of 23°C and 50% RH, and then a peel test is performed using a tensile tester under conditions of 23°C, 50% RH, and a peel rate of 300 mm / min, in which the pressure-sensitive adhesive tape in the laminate is peeled at an angle of 180° from the silicone rubber. After the peel test, the surface of the silicone rubber from which the pressure-sensitive adhesive tape was peeled is washed at least eight times with ethyl acetate, and then TOF-SIMS measurement is performed on the washed surface. The peak intensity of a negative ion in the m / z 26 region relative to the peak intensity (total) of all negative ions (26 / total) is 2.50 × 10 －３or above. Disclosure 2 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a (meth)acrylic copolymer, wherein the pressure-sensitive adhesive layer contains Component A including at least one selected from a silane coupling agent having an aliphatic amino group, a silane coupling agent having a skeleton in which an aliphatic amino group is protected, a compound having a structure derived from a silane coupling agent having an aliphatic amino group, and a compound having a structure derived from a silane coupling agent having a skeleton in which an aliphatic amino group is protected, wherein the content of Component A per 100 parts by mass of the (meth)acrylic copolymer is 8.0 parts by mass or less. Disclosure 3 is the pressure-sensitive adhesive tape of Disclosure 2, wherein the content of Component A per 100 parts by mass of the (meth)acrylic copolymer is 1.5 parts by mass or more. Disclosure 4 is the pressure-sensitive adhesive tape of Disclosure 3, wherein the content of Component A per 100 parts by mass of the (meth)acrylic copolymer is more than 3.0 parts by mass.

[0013] The present disclosure 5 is the pressure-sensitive adhesive tape of disclosure 2, 3, or 4, wherein at least one of the aliphatic amino groups in component A is a primary aliphatic amino group or a secondary aliphatic amino group having an acyclic structure.

[0014] The present disclosure 6 is the pressure-sensitive adhesive tape of disclosure 1, 2, 3, 4, or 5, wherein the (meth)acrylic copolymer has structural units derived from a (meth)acrylic acid alkyl ester, and the structural units derived from the (meth)acrylic acid alkyl ester do not have structural units derived from a (meth)acrylic acid alkyl ester having 2 or less carbon atoms in the alkyl group at the ester terminal, or the structural units derived from the (meth)acrylic acid alkyl ester have structural units derived from a (meth)acrylic acid alkyl ester having 2 or less carbon atoms in the alkyl group at the ester terminal, and the content of structural units derived from a (meth)acrylic acid alkyl ester having 2 or less carbon atoms in the alkyl group at the ester terminal in the structural units derived from the (meth)acrylic acid alkyl ester is 25 mass% or less. Disclosure 7 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, or 6, wherein the structural unit derived from an alkyl (meth)acrylate has a structural unit derived from an alkyl (meth)acrylate, and the structural unit has a structural unit derived from an alkyl (meth)acrylate in which the alkyl group at the ester terminal has 7 carbon atoms.Disclosure 8 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the (meth)acrylic copolymer does not have a constituent unit derived from a carboxy group-containing monomer. Disclosure 9 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the pressure-sensitive adhesive layer contains a component that crosslinks upon electron beam irradiation or ultraviolet light irradiation. Disclosure 10 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the pressure-sensitive adhesive layer contains a radical generator. Disclosure 11 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the pressure-sensitive adhesive layer has a gel fraction of 35 mass% or more.

[0023] The present disclosure 12 is the pressure-sensitive adhesive tape of present disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the pressure-sensitive adhesive layer contains a component that crosslinks upon electron beam irradiation or ultraviolet irradiation, and the pressure-sensitive adhesive layer has a gel fraction of 35% by mass or more. The present disclosure 13 is the pressure-sensitive adhesive tape of present disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, further comprising a separator, wherein the release layer of the separator does not contain an organic fluorine compound. The present disclosure 14 is the pressure-sensitive adhesive tape of present disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, further comprising a separator, wherein, when the separator is peeled 180° from the pressure-sensitive adhesive layer under an environment of 23°C and 50% RH and the surface of the peel interface between the separator and the pressure-sensitive adhesive layer is measured by XPS, the relative intensity of the peak at 103.9 eV is 0.170 or less. Disclosure 15 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, which is used for bonding silicone-based adherends. Disclosure 16 is the pressure-sensitive adhesive tape of Disclosure 15, wherein the silicone-based adherend is an electronic device part, a vehicle part, a construction part, or a medical part. Disclosure 17 is a laminate comprising a structure in which the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 is attached to a silicone-based adherend. Disclosure 18 is an electronic device comprising the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16.The present disclosure 19 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a (meth)acrylic copolymer and a separator, wherein when the separator is peeled at an angle of 180° from the pressure-sensitive adhesive layer under an environment of 23°C and 50% RH and the surface of the peel interface between the separator and the pressure-sensitive adhesive layer is measured by XPS, the relative intensity of the peak at 103.9 eV is 0.170 or less. The present disclosure will be described in detail below.

[0009] The present inventors have investigated the mass-to-charge ratio of the surface of a silicone-based adherend from which a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a (meth)acrylic copolymer has been adhered and then peeled off. As a result, they have found that, when such a mass-to-charge ratio satisfies a specific value, a pressure-sensitive adhesive tape that can exhibit excellent adhesive strength to a silicone-based adherend can be obtained without using a silicone-based pressure-sensitive adhesive or without prior surface treatment of the adherend, and have thus completed the present disclosure.

[0010] The pressure-sensitive adhesive tape of the present disclosure is prepared by laminating the pressure-sensitive adhesive tape to silicone rubber fixed to a SUS304 plate to form a laminate, which is then left to stand for 72 hours in an environment of 23°C and 50% RH. A peel test is then performed using a tensile tester, in which the pressure-sensitive adhesive tape in the laminate is peeled from the silicone rubber at an angle of 180° using a tensile tester under conditions of 23°C, 50% RH, and a peel rate of 300 mm / min. After the peel test, the surface of the silicone rubber from which the pressure-sensitive adhesive tape has been peeled is washed at least eight times with ethyl acetate, and TOF-SIMS measurement is then performed on the washed surface. The lower limit of the peak intensity of the negative ion in the m / z 26 region (26 / total) relative to the peak intensity (total) of all negative ions (hereinafter, this may be simply referred to as "the relative intensity of the peak of the negative ion in the m / z 26 region after the pressure-sensitive adhesive tape has been peeled off") is 2.50 × 10 －３ After peeling off the adhesive tape, the relative intensity of the negative ion peak in the m / z region of 26 was 2.50 × 10 －３As a result, the pressure-sensitive adhesive tape of the present disclosure can exhibit excellent adhesive strength to a silicone-based adherend without using a silicone-based pressure-sensitive adhesive and without prior surface treatment of the adherend. A preferable lower limit of the relative intensity of the negative ion peak in the m / z 26 region after peeling off the pressure-sensitive adhesive tape is 2.60 × 10 －３ , and a more preferable lower limit is 2.70 × 10 －３ Furthermore, the preferred upper limit of the relative intensity of the negative ion peak in the m / z region of 26 after peeling off the adhesive tape is 4.00 × 10 －２ After peeling off the adhesive tape, the relative intensity of the negative ion peak in the m / z region of 26 was 4.00 × 10 －２ By setting the relative intensity of the negative ion peak in the m / z region of 26 after peeling the adhesive tape to 3.50×10 or less, the cohesive force can be increased to avoid cohesive failure that would otherwise result in the adhesive remaining on the adherend, and the bulk strength generally required for adhesive tapes can be ensured. －２ , and a more preferable upper limit is 3.00×10 －２ In this specification, the term "negative ion peak in the m / z region of 26" refers to a peak detected in the m / z range of 25.986 to 26.050.

[0011] The relative intensity of the negative ion peak in the m / z 26 region after peeling off the pressure-sensitive adhesive tape can be measured by the following method. Specifically, first, the surface of a 50 mm × 125 mm SUS304 plate was washed with ethanol and then wiped dry. A film pressure-sensitive adhesive tape (manufactured by Teraoka Seisakusho Co., Ltd., "767") having a silicone-based pressure-sensitive adhesive layer on one side and a pressure-sensitive adhesive layer other than the silicone-based pressure-sensitive adhesive layer on the other side was cut to a size of 30 mm wide and 70 mm long. The separator on the pressure-sensitive adhesive layer other than the silicone-based pressure-sensitive adhesive layer was then peeled off, and the pressure-sensitive adhesive layer was attached to the SUS304 plate. The separator on the silicone-based pressure-sensitive adhesive layer side was then peeled off to expose the silicone-based pressure-sensitive adhesive layer. A 1 mm-thick silicone rubber (manufactured by Togawa Rubber Co., Ltd., K-125(50)) cut to a size of 30 mm wide and 70 mm long was attached to the silicone-based pressure-sensitive adhesive layer to prepare a silicone-based adherend. The pressure-sensitive adhesive tape of the present disclosure was cut to a size of 25 mm wide and 70 mm long. The separator on one side of the cut pressure-sensitive adhesive tape was peeled off, and one side of the pressure-sensitive adhesive tape was backed with the corona-treated surface of a 23 μm-thick polyethylene terephthalate (PET) film. The separator on the other side of the backed pressure-sensitive adhesive tape was peeled off, and the tape was attached to the silicone rubber surface of the silicone-based adherend. A 2 kg roller was then reciprocated once at a speed of 300 mm / min to press the tape together, and the tape was left to stand for 72 hours in an atmosphere of 23°C and 50% RH to produce a laminate. A peel test was performed on the produced laminate in accordance with JIS Z0237 using a tensile tester (Shimadzu Corporation, "AG-IS") at 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°. After the peel test, the surface of the silicone rubber on the silicone-based adherend from which the pressure-sensitive adhesive tape was peeled was washed at least eight times with ethyl acetate, and the washed surface was then subjected to TOF-SIMS measurement. The resulting spectral data was analyzed to determine the peak intensity (26 / total) of the negative ions in the m / z 26 region relative to the peak intensity (total) of all negative ions.

[0012] Specifically, the cleaning operation with ethyl acetate and the TOF-SIMS measurement can be performed by the following methods, etc. Note that, during the following operations, care should be taken not to contaminate the silicone rubber surface from which the adhesive tape has been peeled. Furthermore, when peeling the adhesive tape from a silicone-based adherend in a peel test using a tensile tester, the area where interfacial peeling between the adhesive and the silicone-based adherend occurs as a visual observation is taken as the target area for TOF-SIMS measurement. Note that, if the adhesive layer has undergone cohesive failure over the entire peeled surface of the adhesive tape, the area of ​​cohesive failure can be exposed to liquid nitrogen to cool and solidify, and the cohesively failed adhesive layer can be removed with metal tweezers or a spatula. The above removal operation is repeated until the rubber surface of the silicone-based adherend is visually exposed, and this is taken as the target area for TOF-SIMS measurement.

[0013] (Cleaning Operation) First, the film adhesive tape having a silicone-based pressure-sensitive adhesive layer is peeled off from the silicone rubber. Any peeling method is possible, but it can be done by hand at a speed of approximately 300 mm / min and a peel angle of approximately 90°. After peeling the film adhesive tape having a silicone-based pressure-sensitive adhesive layer from the silicone rubber, the resulting silicone rubber is cut into approximately 1 cm square pieces using a cutter or scissors to prepare a measurement sample. The surface of the measurement sample that had been in contact with the pressure-sensitive adhesive tape of the present disclosure is placed on the surface of the ethyl acetate solution in an aluminum cup with an inner diameter of 5 cm containing 2 mL of ethyl acetate, and then washed with ethyl acetate by shaking back and forth at 1 cm intervals 80 times per minute (i). During this process, the back surface of the sample not involved in the measurement can be pierced with a needle or the like to shake it, or it can be shaken using tweezers. If the sample to be washed comes into contact with the bottom of the aluminum cup during shaking, making the operation difficult, additional ethyl acetate can be added. Another aluminum cup with an inner diameter of 5 cm containing 2 mL of ethyl acetate is prepared, and after washing in the same manner again, the measurement sample is heated in an oven at normal pressure at 80°C for 10 minutes (ii). The above operations (i) and (ii) constitute one set, and a total of four or more sets are performed. Note that new aluminum cups and ethyl acetate are used each time operations (i) and (ii) are performed.

[0014] (TOF-SIMS Measurement) TOF-SIMS measurement can be performed using a time-of-flight secondary ion mass spectrometer (such as "TOF.SIMS5" manufactured by ION-TOF), and the measurement can be performed under the following conditions. From the obtained secondary ion spectrum, the sum (area) of the peaks of negative ions in the region of m / z 26 is divided by the sum (area) of the peaks of all negative ions to calculate the value. <Measurement conditions for TOF-SIMS measurement> Primary ion species: Bi3++ Acceleration voltage: 25 kV Detected ion polarity: negative (negative ion) Measurement range: 500 μm × 500 μm Number of pixels: 128 × 128 (pixels) Number of scans: 25 scans Mass range (m / z): 0 to 850

[0015] The negative ion peak in the m / z 26 region is mainly CN ― Therefore, examples of a method for adjusting the relative intensity of the negative ion peak in the region of m / z 26 after peeling off the pressure-sensitive adhesive tape include a method of adding component A, which will be described later, to the pressure-sensitive adhesive layer, a method of changing the amount or structure of component A, a method of adding an amine-modified silicone compound, and a method of changing the composition of the (meth)acrylic copolymer in the pressure-sensitive adhesive layer.

[0016] The pressure-sensitive adhesive tape of the present disclosure has a pressure-sensitive adhesive layer containing an acrylic copolymer. In this specification, the term "(meth)acrylic" means acrylic or methacrylic.

[0017] The (meth)acrylic copolymer preferably has a structural unit derived from a (meth)acrylic acid alkyl ester (hereinafter, sometimes simply referred to as "structural unit (a)"). Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, isoheptyl (meth)acrylate, and 2-(meth)acrylic acid alkyl ester. Examples of suitable acrylates include ethylhexyl, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, isobornyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and behenyl (meth)acrylate. Among these, from the viewpoint of improving wettability to silicone-based adherends with low surface energy, structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group at the ester end has 3 or more carbon atoms are preferred, and from the viewpoint of avoiding a decrease in cohesive strength that leads to a decrease in adhesive strength and the occurrence of crystalline interactions, structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group at the ester end has 22 or less carbon atoms are preferred. The lower limit for the number of carbon atoms in the alkyl group at the ester end is more preferably 4, the upper limit is more preferably 18, even more preferably 16, still more preferably 12, particularly preferably 10, and most preferably 8.Among these, from the viewpoint of easily ensuring a balance between adhesive strength and cohesive strength to a silicone adherend, it is preferable that the (meth)acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester in which the alkyl group at the ester terminal has 7 carbon atoms. These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more. In addition, in this specification, the term "ester-terminated alkyl group" refers to an alkyl group directly bonded to the oxygen of the ester bond.

[0018] Preferably, the structural unit (a) does not have a structural unit derived from a (meth)acrylic acid alkyl ester in which the alkyl group at the ester terminal has two or less carbon atoms (hereinafter, sometimes simply referred to as "structural unit (a-1)"), or the structural unit (a) has the structural unit (a-1), and the content of the structural unit (a-1) in the structural unit (a) is 25 mass% or less. When the structural unit (a) does not have the structural unit (a-1), or has the structural unit (a-1), and the content of the structural unit (a-1) in the structural unit (a) is 25 mass% or less, the adhesive strength of the pressure-sensitive adhesive tape of the present disclosure to silicone-based adherends is further improved. The upper limit of the content of the structural unit (a-1) relative to 100% by mass of the structural unit (a) is more preferably 20% by mass, even more preferably 15% by mass, and even more preferably 10% by mass. It is most preferable that the structural unit (a) does not contain the structural unit (a-1).

[0019] The preferred lower limit of the content of the structural unit (a) in the (meth)acrylic copolymer is 50% by mass. When the content of the structural unit (a) is 50% by mass or more, the adhesive strength of the pressure-sensitive adhesive tape of the present disclosure to a silicone-based adherend is further improved. Furthermore, the content of the structural unit (a) may be 100% by mass, i.e., the (meth)acrylic copolymer may be composed only of the structural unit (a), but from the viewpoint that it is preferable to contain a structural unit derived from a polar group-containing monomer described below in order to improve adhesive strength and holding power, the preferred upper limit is 99.9% by mass.

[0020] The (meth)acrylic copolymer may contain at least one structural unit selected from the group consisting of structural units derived from hydroxyl group-containing monomers, structural units derived from amino group-containing monomers, structural units derived from amide group-containing monomers (excluding N,N-disubstituted amide skeletons), structural units derived from alkenyl group-containing monomers, and structural units derived from alkynyl group-containing monomers (hereinafter, these structural units may be simply referred to as "structural unit (b)"). When the (meth)acrylic copolymer contains the structural unit (b), the polarity of the pressure-sensitive adhesive layer is increased, further increasing the cohesive strength, thereby improving the adhesive strength and high-temperature holding power. Furthermore, when a crosslinked structure is formed by chemically crosslinking the functional groups such as hydroxyl groups, amino groups, amide groups, alkenyl groups, and alkynyl groups, the cohesive strength of the pressure-sensitive adhesive layer is further increased, thereby further improving the adhesive strength and holding power. Among these, from the viewpoints of avoiding reaction with a silane coupling agent having an aliphatic amino group or a silane coupling agent having a skeleton in which the aliphatic amino group is protected, and ensuring the coatability of the pressure-sensitive adhesive solution and the performance stability over time of the pressure-sensitive adhesive layer, it is preferable that the (meth)acrylic copolymer has structural units derived from a hydroxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer (excluding an N,N-disubstituted amide skeleton).

[0021] Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of the amino group-containing monomer include 2-dimethylaminoethyl (meth)acrylate and N-{3-(dimethylamino)propyl}acrylamide. Examples of the amide group-containing monomer (excluding the N,N-disubstituted amide skeleton) include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, N-heptyl(meth)acrylamide, N-octyl(meth)acrylamide, and N-(2-ethylhexyl)(meth)acrylamide.

[0022] When the (meth)acrylic copolymer contains the structural unit (b), the preferred upper limit of the total content of the structural unit (b) in the (meth)acrylic copolymer is 20% by mass. By having the total content of the structural unit (b) be 20% by mass or less, the polarity of the pressure-sensitive adhesive layer is further reduced, thereby reducing the surface energy of the pressure-sensitive adhesive layer and further improving the adhesive strength to silicone-based adherends. Furthermore, reaction with silane coupling agents having aliphatic amino groups or silane coupling agents having a backbone with a protected aliphatic amino groups is minimized, ensuring the coatability of the pressure-sensitive adhesive solution and the long-term performance stability of the pressure-sensitive adhesive layer. The more preferred upper limit of the total content of the structural unit (b) is 15% by mass, even more preferred is 10% by mass, even more preferred is 5.0% by mass, and particularly preferred is 1.0% by mass. The lower limit of the total content of the structural unit (b) in the (meth)acrylic copolymer is not particularly limited, and may be 0% by mass or greater than 0% by mass. When the lower limit of the total content of the structural unit (b) is greater than 0% by mass, it is, for example, 0.1% by mass. Specific examples of the total content of the structural unit (b) in the (meth)acrylic copolymer include ranges such as 0% by mass or more and 20% by mass or less, 0% by mass or more and 15% by mass or less, 0% by mass or more and 10% by mass or less, 0% by mass or more and 5.0% by mass or less, 0% by mass or more and 1.0% by mass or less, 0.1% by mass or more and 20% by mass or less, 0.1% by mass or more and 15% by mass or less, 0.1% by mass or more and 10% by mass or less, 0.1% by mass or more and 5.0% by mass or less, and 0.1% by mass or more and 1.0% by mass or less.

[0023] The (meth)acrylic copolymer may have a structural unit derived from a carboxyl group-containing monomer within a range that does not impair the effects of the present disclosure. When the (meth)acrylic copolymer has a structural unit derived from a carboxyl group-containing monomer, the polarity of the pressure-sensitive adhesive layer increases, further increasing the cohesive strength, thereby improving the adhesive strength and the high-temperature holding power. Furthermore, when a crosslinked structure is formed by chemically crosslinking the functional groups, the cohesive strength of the pressure-sensitive adhesive is further increased, thereby further improving the adhesive strength and holding power.

[0024] Examples of the carboxy group-containing monomer include (meth)acrylic acid and 2-acryloyloxyethyl succinate.

[0025] When the (meth)acrylic copolymer contains structural units derived from the carboxyl group-containing monomer, the content of structural units derived from the carboxyl group-containing monomer in the (meth)acrylic copolymer is preferably less than 1.0% by mass. By having the content of structural units derived from the carboxyl group-containing monomer less than 1.0% by mass, reaction with a silane coupling agent having an aliphatic amino group or a silane coupling agent having a backbone with a protected aliphatic amino group can be minimized, ensuring the coatability of the pressure-sensitive adhesive solution and the long-term performance stability of the pressure-sensitive adhesive layer. When the acrylic acid content was 1.0% by mass, a rapid increase in viscosity was observed when a silane coupling agent having an aliphatic amino group was blended into the acrylic copolymer solution, making it substantially difficult to form a pressure-sensitive adhesive layer suitable for evaluation. The upper limit of the content of structural units derived from the carboxyl group-containing monomer is more preferably 0.5% by mass, even more preferably 0.3% by mass, even more preferably 0.1% by mass, and particularly preferably 0.05% by mass. It is most preferred that the (meth)acrylic copolymer does not contain structural units derived from the carboxyl group-containing monomer.

[0026] The (meth)acrylic copolymer may contain structural units derived from N,N-disubstituted amide group-containing monomers within the scope of the present disclosure. When the (meth)acrylic copolymer contains structural units derived from N,N-disubstituted amide group-containing monomers, the polarity of the pressure-sensitive adhesive layer increases, further increasing the cohesive strength, thereby improving the adhesive strength and the high-temperature holding power.

[0027] Examples of the N,N-disubstituted amide group-containing monomer include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dibutyl(meth)acrylamide, N-(meth)acryloylpyrrolidine, N-(meth)acryloylmorpholine, N-methyl-N-vinylacetamide, and N-vinylpyrrolidone.

[0028] The preferred lower limit of the total content of structural units derived from N,N-disubstituted amide group-containing monomers in the (meth)acrylic copolymer is 3.0% by mass, and the preferred upper limit is 50% by mass. When the content of structural units derived from N,N-disubstituted amide group-containing monomers is 3.0% by mass or more, the cohesive strength of the PSA is more likely to be improved, and the adhesive strength and high-temperature holding power of the PSA tape of the present disclosure are further improved. When the content of structural units derived from N,N-disubstituted amide group-containing monomers is 50% by mass or less, it is possible to suppress a decrease in initial adhesion and adhesive strength due to an excessive increase in cohesive strength. The preferred lower limit of the structural units derived from N,N-disubstituted amide group-containing monomers is 5.0% by mass, an even more preferred lower limit is 10% by mass, and an even more preferred lower limit is 15% by mass, and a more preferred upper limit is 45% by mass, an even more preferred upper limit is 40% by mass, and an even more preferred upper limit is 35% by mass.

[0029] The (meth)acrylic copolymer may have structural units other than the structural unit (a), the structural unit (b), the structural unit derived from the carboxy group-containing monomer, and the structural unit derived from the N,N-disubstituted amide group-containing monomer, within a range that does not impair the effects of the present disclosure.

[0030] The (meth)acrylic copolymer preferably has a weight-average molecular weight (Mw) of 400,000 or more, with a lower limit of 400,000 and a higher limit of 2,000,000. When the (meth)acrylic copolymer has a weight-average molecular weight (Mw) of 400,000 or more, the adhesive strength and holding power of the pressure-sensitive adhesive tape of the present disclosure are further improved. When the (meth)acrylic copolymer has a weight-average molecular weight (Mw) of 2,000,000 or less, the pressure-sensitive adhesive layer does not become too hard, and the adhesive strength of the pressure-sensitive adhesive tape of the present disclosure is further increased. The weight-average molecular weight (Mw) of the (meth)acrylic copolymer more preferably has a lower limit of 500,000, an even more preferred lower limit of 600,000, and a more preferred upper limit of 1,600,000, an even more preferred upper limit of 1,200,000. Specific examples of the weight average molecular weight (Mw) of the (meth)acrylic copolymer include ranges of 400,000 to 2,000,000, 400,000 to 1,600,000, 400,000 to 1,200,000, 500,000 to 2,000,000, 500,000 to 1,600,000, 500,000 to 1,200,000, 600,000 to 2,000,000, 600,000 to 1,600,000, and 600,000 to 1,200,000. In this specification, the term "weight average molecular weight" refers to the weight average molecular weight measured by gel permeation chromatography (GPC) as a polystyrene-equivalent molecular weight. Specifically, the weight-average molecular weight of the (meth)acrylic copolymer can be measured using, for example, a Waters "2690 Separations Module" measuring instrument, a Showa Denko "GPC KF-806L" column, and ethyl acetate as a solvent under the conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0031] The preferred lower limit of the content of the (meth)acrylic copolymer in the pressure-sensitive adhesive layer is 50% by mass, and the preferred upper limit is 99.5% by mass. When the content of the (meth)acrylic copolymer is 50% by mass or more, it is possible to exhibit the general physical properties required of a pressure-sensitive adhesive, such as adhesive strength and holding power. When the content of the (meth)acrylic copolymer is 99.5% by mass or less, the amount of components necessary for silicone adhesion is ensured, and sufficient silicone adhesive strength can be exhibited. The more preferred lower limit of the content of the (meth)acrylic copolymer is 60% by mass, and the more preferred upper limit is 99% by mass, and even more preferred lower limit is 70% by mass, and even more preferred upper limit is 98.5% by mass, and even more preferred lower limit is 75%. Even more preferred upper limit is 98% by mass, and particularly preferred lower limit is 80% by mass, and particularly preferred upper limit is 97.5% by mass.

[0032] The polymerization method for synthesizing the (meth)acrylic copolymer may be a conventionally known method in which monomers from which the above-mentioned structural units are derived are subjected to a radical reaction in the presence of a polymerization initiator, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, etc. Among these, solution polymerization is preferred because of its ease of synthesis.

[0033] When solution polymerization is used as the polymerization method, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, diethyl ether, etc. These reaction solvents may be used alone or in combination of two or more.

[0034] Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0035] The pressure-sensitive adhesive layer preferably contains a component A containing at least one selected from a silane coupling agent having an aliphatic amino group (hereinafter sometimes referred to as "component A-1"), a silane coupling agent having a skeleton in which an aliphatic amino group is protected (hereinafter sometimes referred to as "component A-2"), a compound having a structure derived from a silane coupling agent having an aliphatic amino group (hereinafter sometimes referred to as "component A-3"), and a compound having a structure derived from a silane coupling agent having a skeleton in which an aliphatic amino group is protected (hereinafter sometimes referred to as "component A-4"). When the pressure-sensitive adhesive layer contains the component A, the adhesive strength of the pressure-sensitive adhesive tape of the present disclosure to silicone-based adherends is further improved.

[0036] The number of series of the aliphatic amino group in Component A is not particularly limited. However, from the viewpoint of easily exhibiting adhesive strength to silicone-based adherends, it is preferable that at least one of the aliphatic amino groups in Component A is a primary aliphatic amino group or a secondary aliphatic amino group, more preferably a primary aliphatic amino group or a secondary aliphatic amino group with an acyclic structure, and even more preferably a primary aliphatic amino group. In this specification, the term "secondary aliphatic amino group with an acyclic structure" refers to a secondary aliphatic amino group in which the nitrogen atom in the amino group is not contained in a cyclic structure. Furthermore, the structure of the hydrocarbon chain constituting the aliphatic amino group is not particularly limited, and may be linear or branched, or may have a cyclic structure. Furthermore, Component A may have one or more alkoxysilyl groups, and the alkoxysilyl group may be a monoalkoxysilyl group, a dialkoxysilyl group, or a trialkoxy group.

[0037] Component A-1 is not particularly limited as long as it is a silane coupling agent having an aliphatic amino group, and may have one or more aliphatic amino groups. Furthermore, the number of aliphatic amino groups possessed by Component A-1 is not particularly limited. However, as described above, from the viewpoint of facilitating the development of adhesive strength to silicone-based adherends, it is preferable that the silane coupling agent contain at least one selected from the group consisting of a primary aliphatic amino group and a secondary aliphatic amino group. It is more preferable that the silane coupling agent contain at least one selected from the group consisting of a primary aliphatic amino group and a secondary aliphatic amino group having an acyclic structure, and it is even more preferable that the silane coupling agent contain a primary aliphatic amino group. Furthermore, as described above, the structure of the hydrocarbon chain constituting the aliphatic amino group is not particularly limited, and it may be linear or branched, or may have a cyclic structure. Furthermore, the structure of the hydrocarbon chain between the amino group and the alkoxysilyl group is not particularly limited. However, if the number of carbon atoms in the hydrocarbon chain is too small, the steric hindrance between the amino group and the alkoxysilyl group becomes significant, making it difficult to develop silicone adhesive strength. Therefore, it is preferable that the number of carbon atoms between the amino group and the alkoxysilyl group is 3 or more. Furthermore, the upper limit of the number of carbon atoms between the amino group and the alkoxysilyl group is not particularly limited, but a preferred upper limit is 8. Specifically, a propylene group or an octylene group is preferred, and a propylene group is more preferred. In addition, as described above, Component A-1 may have one or more alkoxysilyl groups, and the alkoxysilyl group may be a monoalkoxysilyl group, a dialkoxysilyl group, or a trialkoxy group.

[0038] Examples of component A-1 include N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-8-aminooctyltrimethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinylbenzylaminoethylaminopropyltrimethoxysilane, N,N'-bis[3-(trimethoxysilyl)propyl]-1,2-ethanediamine, and X-12-972F manufactured by Shin-Etsu Chemical Co., Ltd.

[0039] The skeleton in which the aliphatic amino group in Component A-2 is protected may have an aliphatic group or an aromatic group as a protecting group, as long as the effects of the present disclosure are not impaired. Examples of the skeleton in which the aliphatic amino group is protected include a ketimine skeleton and an aldimine skeleton. Component A-2 may have one skeleton in which the aliphatic amino group is protected, or two or more skeletons. Component A-2 may have one or more alkoxysilyl groups, and the alkoxysilyl group may be a monoalkoxysilyl group, a dialkoxysilyl group, or a trialkoxy group.

[0040] Examples of the component A-2 include 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-[3-(triethoxysilylpropyl)]benzaldehydeimine, and the like.

[0041] Examples of the component A-3 include a polymer of the component A-1.

[0042] Examples of the component A-4 include a polymer of the component A-2.

[0043] The preferred upper limit of the content of component A relative to 100 parts by mass of the (meth)acrylic copolymer is 8.0 parts by mass. When the content of component A is 8.0 parts by mass or less, it is possible to prevent the silane coupling agent from precipitating in the pressure-sensitive adhesive layer, and to further suppress a decrease in the adhesive strength of the pressure-sensitive adhesive tape of the present disclosure. The more preferred upper limit of the content of component A is 7.0 parts by mass, even more preferred is 6.0 parts by mass, and even more preferred is 5.0 parts by mass. The preferred lower limit of the content of component A is 1.5 parts by mass. When the content of component A is 1.5 parts by mass or more, the adhesive strength of the pressure-sensitive adhesive tape of the present disclosure to silicone-based adherends is further improved. The content of component A is more preferably 2.0 parts by mass or more, even more preferably 2.5 parts by mass or more, even more preferably more than 3.0 parts by mass, particularly preferably 3.2 parts by mass or more, particularly more preferably 3.5 parts by mass or more, and especially preferably 4.0 parts by mass or more. Specific examples of the content of Component A relative to 100 parts by mass of the (meth)acrylic copolymer include 1.5 parts by mass or more and 8.0 parts by mass or less, 1.5 parts by mass or more and 7.0 parts by mass or less, 1.5 parts by mass or more and 6.0 parts by mass or less, 1.5 parts by mass or more and 5.0 parts by mass or less, 2.0 parts by mass or more and 8.0 parts by mass or less, 2.0 parts by mass or more and 7.0 parts by mass or less, 2.0 parts by mass or more and 6.0 parts by mass or less, 2.0 parts by mass or more and 5.0 parts by mass or less, 2.5 parts by mass or more and 8.0 parts by mass or less, 2.5 parts by mass or more and 7.0 parts by mass or less, 2.5 parts by mass or more and 6.0 parts by mass or less, 2.5 parts by mass or more and 5.0 parts by mass or less, and more than 3.0 parts by mass or more and 8.0 parts by mass or less. Lower, greater than 3.0 parts by mass and less than or equal to 7.0 parts by mass, greater than 3.0 parts by mass and less than or equal to 6.0 parts by mass, greater than 3.0 parts by mass and less than or equal to 5.0 parts by mass, greater than or equal to 3.2 parts by mass and less than or equal to 8.0 parts by mass, greater than or equal to 3.2 parts by mass and less than or equal to 6.0 parts by mass, greater than or equal to 3.2 parts by mass and less than or equal to 5.0 parts by mass, 3.5 parts by mass 8.0 parts by mass or less, 3.5 parts by mass or more and 7.0 parts by mass or less, 3.5 parts by mass or more and 6.0 parts by mass, 3.5 parts by mass or more and 5.0 parts by mass, 4.0 parts by mass or more and 8.0 parts by mass, 4.0 parts by mass or more and 7.0 parts by mass or less, 4.0 parts by mass or more and 5.0 parts by mass or less, and the like.

[0044] The pressure-sensitive adhesive layer may contain other additives such as a tackifier resin, a softener, and an inorganic filler, as needed, within the scope of not impairing the effects of the present disclosure.

[0045] Since device materials are usually exposed to high-temperature environments during use, it is preferable that a pressure-sensitive adhesive tape for adhering a silicone material has high-temperature holding power, and from this viewpoint, it is preferable that the components in the pressure-sensitive adhesive layer have a crosslinked structure. By forming a crosslinked structure in the components in the pressure-sensitive adhesive layer, it becomes easier to adjust the gel fraction of the pressure-sensitive adhesive layer, which will be described later, to an appropriate range, thereby further improving the cohesive strength of the pressure-sensitive adhesive layer and further improving the high-temperature holding power of the pressure-sensitive adhesive tape of the present disclosure.

[0046] Examples of methods for crosslinking components in the pressure-sensitive adhesive layer include radiation crosslinking such as electron beam irradiation, ultraviolet irradiation, and gamma ray irradiation, chemical crosslinking, physical crosslinking, etc. Among these, electron beam irradiation and ultraviolet irradiation are preferred from the viewpoints of enabling crosslinking to proceed without introducing polar functional groups into the pressure-sensitive adhesive layer, thereby enabling a pressure-sensitive adhesive layer with low polarity, further improving adhesive strength to silicone-based adherends, providing the pressure-sensitive adhesive layer with superior high-temperature retention, and ensuring the stability of the pressure-sensitive adhesive solution over time, and electron beam irradiation is more preferred from the viewpoint of minimizing the amount of blended components.

[0047] Examples of a method for crosslinking the components in the pressure-sensitive adhesive layer by electron beam irradiation include irradiating the pressure-sensitive adhesive tape with electron beams using an electron beam irradiation device (such as "EBC-200" manufactured by NHV Corporation).

[0048] Examples of methods for crosslinking components in the pressure-sensitive adhesive layer by ultraviolet irradiation include irradiating a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a radical generator with ultraviolet light having a wavelength of 365 nm using a chemical lamp (such as "FL20S-BL" manufactured by Toshiba Corporation). Examples of radical generators contained in the pressure-sensitive adhesive layer include benzophenone and 4,4'-bis(dimethylamino)benzophenone.

[0049] The pressure-sensitive adhesive layer preferably contains a component that crosslinks upon irradiation with an electron beam or ultraviolet light (hereinafter, sometimes simply referred to as an "electron beam or other cross-linking component.") By containing the electron beam or other cross-linking component, the pressure-sensitive adhesive layer is more likely to crosslink upon irradiation with an electron beam or ultraviolet light, which makes it easier for the pressure-sensitive adhesive layer to have better high-temperature holding power.

[0050] Examples of the component that crosslinks upon electron beam irradiation include (meth)acrylic monomers and allyl group-containing compounds (which may exclude the (meth)acrylic copolymers). Specific examples include ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and triallyl isocyanurate. Examples of the component that crosslinks upon ultraviolet irradiation include (meth)acrylic monomers and allyl group-containing compounds (which may exclude the (meth)acrylic copolymers). Specific examples include ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and triallyl isocyanurate.

[0051] When the pressure-sensitive adhesive layer contains the electron beam or other crosslinking component, the preferred lower limit of the content of the electron beam or other crosslinking component relative to 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass and the preferred upper limit is 15 parts by mass. Having the electron beam or other crosslinking component in a content of 0.1 parts by mass or more makes it easier for the pressure-sensitive adhesive layer to have better high-temperature holding power. Having the electron beam or other crosslinking component in a content of 15 parts by mass or less can suppress a decrease in adhesive power due to bleed-out of the electron beam or other crosslinking component or excessive crosslinking. A more preferred lower limit of the content of the electron beam or other crosslinking component is 0.5 parts by mass, a more preferred upper limit is 12 parts by mass, an even more preferred lower limit is 1.0 part by mass, and an even more preferred upper limit is 10 parts by mass. Since the pressure-sensitive adhesive layer can exhibit excellent high-temperature holding power even without containing the electron beam or other crosslinking component, the pressure-sensitive adhesive layer does not necessarily need to contain the electron beam or other crosslinking component. The content of the electron beam or other crosslinking component may be, for example, in the range of from 0 to 15 parts by mass, from 0 to 12 parts by mass, from 0 to 10 parts by mass, from 0.1 to 15 parts by mass, from 0.1 to 12 parts by mass, from 0.1 to 10 parts by mass, from 0.5 to 15 parts by mass, from 0.5 to 12 parts by mass, from 0.5 to 10 parts by mass, from 1.0 to 15 parts by mass, from 1.0 to 12 parts by mass, or from 1.0 to 10 parts by mass.

[0052] In order to facilitate the crosslinking of the pressure-sensitive adhesive layer by electron beam irradiation or ultraviolet irradiation, the (meth)acrylic copolymer may contain an alkenyl group such as a vinyl group, an allyl group, or a styryl group, or a (meth)acryloyl group. In this specification, the term "(meth)acryloyl group" refers to an acryloyl group or a methacryloyl group.

[0053] The pressure-sensitive adhesive layer preferably contains a radical generator, which makes it easier for crosslinking of the pressure-sensitive adhesive layer by ultraviolet irradiation to proceed.

[0054] Examples of the radical generator include benzophenone-based, benzil ketal-based, α-hydroxyketone-based, α-aminoketone-based, and α-acylphosphinoxide-based photoradical generators, with benzophenone-based materials being preferred. Specific examples of benzophenone-based photoradical generators include benzophenone and 4,4'-bis(dimethylamino)benzophenone.

[0055] The preferred lower limit of the content of the radical generator relative to 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass, and the preferred upper limit is 10 parts by mass. When the content of the radical generator is 0.1 parts by mass or more, the pressure-sensitive adhesive layer is more likely to have excellent high-temperature retention. When the content of the radical generator is 10 parts by mass or less, it is possible to suppress a decrease in adhesive strength due to bleeding out of the radical generator or excessive crosslinking. The more preferred lower limit of the content of the radical generator is 0.5 parts by mass, and the more preferred upper limit is 8 parts by mass, and even more preferred lower limit is 1 part by mass, and even more preferred upper limit is 5 parts by mass. Furthermore, preferred contents of the radical generator include, for example, ranges of 0.1 parts by mass or more and 10 parts by mass or less, 0.1 parts by mass or more and 8 parts by mass or less, 0.1 parts by mass or more and 5 parts by mass or less, 0.5 parts by mass or more and 10 parts by mass or less, 0.5 parts by mass or more and 8 parts by mass or less, 0.5 parts by mass or more and 5 parts by mass or less, 1 part by mass or more and 10 parts by mass or less, 1 part by mass or more and 8 parts by mass or less, and 1 part by mass or more and 5 parts by mass or less.

[0056] The pressure-sensitive adhesive layer preferably has a gel fraction of 35% by mass or less. A gel fraction of 35% by mass or more in the pressure-sensitive adhesive layer further improves the cohesive strength of the pressure-sensitive adhesive layer, thereby further improving the high-temperature holding power of the pressure-sensitive adhesive tape of the present disclosure. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 40% by mass, an even more preferred lower limit is 45% by mass, and an even more preferred lower limit is 50% by mass. Furthermore, a preferred upper limit of the gel fraction of the pressure-sensitive adhesive layer is 90% by mass. A gel fraction of 90% by mass or less in the pressure-sensitive adhesive layer allows the layer to exhibit high holding power and required adhesive strength. A more preferred upper limit of the gel fraction of the pressure-sensitive adhesive layer is 85% by mass, an even more preferred upper limit is 80% by mass, and an even more preferred upper limit is 75% by mass. Specific examples of preferred gel fractions of the pressure-sensitive adhesive layer include ranges of 35% by mass or more and 90% by mass or less, 35% by mass or more and 85% by mass or less, 35% by mass or more and 80% by mass or less, 35% by mass or more and 75% by mass or less, 40% by mass or more and 90% by mass or less, 40% by mass or more and 85% by mass or less, 40% by mass or more and 80% by mass or less, 40% by mass or more and 75% by mass or less, 45% by mass or more and 90% by mass or less, 45% by mass or more and 85% by mass or less, 45% by mass or more and 80% by mass or less, 45% by mass or more and 75% by mass or less, 50% by mass or more and 90% by mass or less, 50% by mass or more and 85% by mass or less, 50% by mass or more and 80% by mass or less, and 50% by mass or more and 75% by mass or less.

[0057] The gel fraction of the pressure-sensitive adhesive layer can be measured by the following method. Specifically, W0 (g) of pressure-sensitive adhesive from the pressure-sensitive adhesive layer is scraped off and immersed in 50 mL of ethyl acetate, and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, a metal mesh (opening #200 mesh) is used to separate the ethyl acetate and the pressure-sensitive adhesive that has absorbed the ethyl acetate and swollen. The separated pressure-sensitive adhesive is dried at 110°C for 1 hour. The mass of the pressure-sensitive adhesive including the metal mesh after drying is measured, and the gel fraction (mass %) is calculated using the following formula (1): Gel fraction (mass %) = 100 × (W １ -W ２ ) / W ０ (1) (W ０ : initial adhesive mass, W １ : adhesive mass including metal mesh after drying, W ２: initial mass of the metal mesh)

[0058] The gel fraction of the pressure-sensitive adhesive layer can also be measured by preparing a test piece consisting of only the pressure-sensitive adhesive layer, or a test piece having a substrate and a pressure-sensitive adhesive layer, and then using the prepared test piece. Specifically, the test piece is immersed in 50 mL of ethyl acetate and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, a metal mesh (opening #200 mesh) is used to separate the ethyl acetate from the test piece that has absorbed the ethyl acetate and swollen. The separated test piece is dried at 110°C for 1 hour. The mass of the dried test piece including the metal mesh is measured, and the gel fraction (mass%) is calculated using the following formula (2). Note that the test piece does not have a separator. When the test piece does not have a substrate, the W in the following formula (2) is used. ０ The calculation is performed assuming that the gel fraction is 0. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (2) (W ０ : Mass of the base material layer, W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0059] Methods for adjusting the gel fraction of the pressure-sensitive adhesive layer within the above range include, for example, adjusting the composition of the (meth)acrylic copolymer, adjusting the crosslinking conditions of the components in the pressure-sensitive adhesive layer, and adjusting the type and amount of additives such as silane coupling agents. Examples of methods for adjusting the crosslinking conditions include, for example, adjusting the irradiation intensity, irradiation time, and acceleration voltage of electron beam irradiation in the case of crosslinking by electron beam irradiation, and adjusting the irradiation intensity and irradiation time of ultraviolet light, which is an energy ray that promotes crosslinking, and removing oxygen, which inhibits the reaction. When chemical crosslinking is used, examples include adjusting the reactivity and amount of the crosslinking agent, and the reactivity and amount of the functional group in the (meth)acrylic copolymer that reacts with the crosslinking agent.

[0060] The preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 5 μm, and the preferred upper limit is 200 μm. By having the thickness of the pressure-sensitive adhesive layer within this range, the resulting pressure-sensitive adhesive tape can achieve both sufficient adhesive strength and ease of handling. The more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 10 μm, and even more preferred is 15 μm, and the more preferred upper limit is 150 μm, and even more preferred is 125 μm, and even more preferred is 100 μm. Specific examples of the thickness of the pressure-sensitive adhesive layer include 5 μm or more and 200 μm or less, 5 μm or more and 150 μm or less, 5 μm or more and 125 μm or less, 5 μm or more and 100 μm or less, 10 μm or more and 200 μm or less, 10 μm or more and 150 μm or less, 10 μm or more and 125 μm or less, 10 μm or more and 100 μm or less, 15 μm or more and 200 μm or less, 15 μm or more and 150 μm or less, 15 μm or more and 125 μm or less, and 15 μm or more and 100 μm or less.

[0061] The pressure-sensitive adhesive tape of the present disclosure may have layers other than the pressure-sensitive adhesive layer, such as a substrate, to the extent that the effects of the present disclosure are not impaired. Also, the pressure-sensitive adhesive tape may have one or more pressure-sensitive adhesive layers of a type different from the above-mentioned pressure-sensitive adhesive layer.

[0062] The pressure-sensitive adhesive tape of the present disclosure may have a separator on at least one surface of the pressure-sensitive adhesive layer. That is, the pressure-sensitive adhesive tape of the present disclosure may be a pressure-sensitive adhesive tape having a separator on one surface of the pressure-sensitive adhesive layer, or a pressure-sensitive adhesive tape having separators on both surfaces of the pressure-sensitive adhesive layer.

[0063] The separator substrate used in the separator is not particularly limited, and any substrate commonly used for separators can be appropriately selected and used. Examples include plastic films such as polyester, polyethylene, polypropylene, polymethylpentene, and polycarbonate; metal foils such as aluminum and stainless steel; and paper substrates such as glassine paper, fine paper, coated paper, impregnated paper, synthetic paper, and kraft paper. Among these, polyester is preferred from the viewpoint of suppressing the inclusion of foreign matter from the separator. Examples of the polyester include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).

[0064] The separator preferably has a release layer. By including a release layer in the separator, the separator can be easily peeled from the pressure-sensitive adhesive layer, and the function and appearance of the pressure-sensitive adhesive tape of the present disclosure can be prevented from being impaired after the separator is peeled. When the pressure-sensitive adhesive tape of the present disclosure has the separator on both sides, only the separator on one side may have the release layer, or both separators may have the release layer.

[0065] The release layer is not particularly limited, but a release layer that does not contain an organic fluorine compound is preferred. In this specification, "does not contain an organic fluorine compound" means that the content of the organic fluorine compound is below the detection limit when the surface of the separator on the release layer side is measured by XPS, TOF-SIMS, or the like. The absence of an organic fluorine compound in the release layer makes it possible to obtain a pressure-sensitive adhesive tape with a reduced content of organic fluorine compounds. Note that, in conventional pressure-sensitive adhesive tapes used for adhesion to silicone-based adherends, if the release layer of the separator does not contain an organic fluorine compound, it has been difficult to peel the separator from the adhesive layer that the separator protects. This has led to a problem that the release layer of the separator in the pressure-sensitive adhesive tape must contain a fluorine compound. On the other hand, in the pressure-sensitive adhesive tape of the present disclosure, even if the release layer of the separator does not contain an organic fluorine compound, the separator can be easily peeled from the adhesive layer. Therefore, the pressure-sensitive adhesive tape of the present disclosure is desirable from this perspective as well.

[0066] When the separator is peeled 180° from the pressure-sensitive adhesive layer under an environment of 23°C and 50% RH and the surface of the peel interface with the pressure-sensitive adhesive layer is subjected to XPS analysis, the relative intensity of the peak at 103.9 eV (hereinafter, sometimes simply referred to as the "relative intensity in XPS analysis of the separator") is preferably 0.170. When the relative intensity in XPS analysis of the separator is 0.170 or less, the separator can be more suitably used to protect the pressure-sensitive adhesive layer, and can be more easily peeled when using the pressure-sensitive adhesive tape of the present disclosure. As a result, the pressure-sensitive adhesive tape of the present disclosure can be more suitably used in practice. The upper limit of the relative intensity in XPS analysis of the separator is more preferably 0.160, and even more preferably 0.150. The lower limit of the relative intensity in XPS measurement of the separator is not particularly limited, but is preferably 0.010, more preferably 0.020, and even more preferably 0.030. Specific examples of the relative intensity in XPS measurement of the separator include ranges of 0.010 to 0.170, 0.010 to 0.160, 0.010 to 0.150, 0.020 to 0.170, 0.020 to 0.160, 0.020 to 0.150, 0.030 to 0.170, 0.030 to 0.160, and 0.030 to 0.150.

[0067] The relative intensity of the separator in XPS measurement can be measured by the following method. That is, first, if necessary, the separator on the side of the pressure-sensitive adhesive tape that is not to be subjected to XPS measurement is peeled from the pressure-sensitive adhesive layer, and then a 2 kg rubber roller is used to roll the tape back and forth once at a speed of 300 mm / min, thereby pressing the tape against a 23 μm-thick polyethylene terephthalate (PET) film or the like to prepare a backing test piece. Note that this step is unnecessary if the pressure-sensitive adhesive tape has the separator on only one side. Next, the separator is peeled from the test piece using a tensile tester (Shimadzu Corporation, "AG-IS") in accordance with JIS Z0237 under conditions of 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°. Then, narrow scan analysis of C1s, O1s, and Si2p in XPS measurement is performed on the peel interface between the separator peeled from the pressure-sensitive adhesive layer and the separator under the following conditions. After calibration with the C1s peak top set to 284.8 eV, the maximum value within the measurement range of Si2p is set to 1 and the minimum value is set to 0, and the relative intensity of the peak at 103.9 eV is determined, thereby obtaining the relative intensity in the XPS measurement of the separator. <XPS measurement conditions> Measurement device: PHI5000VersaProbeII (manufactured by ULVAC-PHI) X-ray source: Al Kα ray (1486.6 eV) Photoelectron take-off angle: 45 degrees Pass energy: 23.5 eV (Si2p), 58.7 eV (C1s, O1s) Measurement setting range: 94.0 eV to 114.0 eV (Si2p), 278.0 eV to 298.0 eV (C1s), 298.0 eV to 523.0 eV (O1s) Step width: 0.1 eV (Si2p), 0.125 eV (C1s, O1s) Number of sweeps: 3 (Si2p), 2 (C1s), 1 (O1s) Number of cycles: 10

[0068] The present disclosure also includes a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a (meth)acrylic copolymer and a separator, wherein when the separator is peeled at an angle of 180° from the pressure-sensitive adhesive layer under an environment of 23°C and 50% RH and the surface of the peel interface between the separator and the pressure-sensitive adhesive layer is measured by XPS, the relative intensity of the peak at 103.9 eV is 0.17 or less.

[0069] When the pressure-sensitive adhesive tape has separators on both sides, the relative intensity of the separator in XPS measurement may satisfy the above-mentioned range for only one separator, or may satisfy the above-mentioned range for both separators. When the pressure-sensitive adhesive tape has separators on both sides, the relative intensity of the separator in XPS measurement more preferably satisfies the above-mentioned range for both separators.

[0070] The preferred lower limit of the thickness of the separator (total thickness of the separator substrate and release layer) is 12 μm. When the thickness of the separator is 12 μm or more, damage from unintentional bending or impact when handling the adhesive tape can be suppressed, and the resulting adhesive tape can be further prevented from losing its appearance or function after the separator is peeled off. The more preferred lower limit of the thickness of the separator is 19 μm, and the even more preferred lower limit is 25 μm. Furthermore, the upper limit of the thickness of the separator is not particularly limited, but the practical upper limit is 200 μm.

[0071] The pressure-sensitive adhesive tape of the present disclosure may be a supported-type pressure-sensitive adhesive tape having a substrate other than the separator substrate, or a non-supported-type pressure-sensitive adhesive tape having no substrate other than the separator substrate.Furthermore, the pressure-sensitive adhesive tape of the present disclosure may be a double-sided tape configured to include another pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer that can exhibit excellent adhesive strength to silicone-based adherends.

[0072] The method for producing the pressure-sensitive adhesive tape of the present disclosure is not particularly limited, and a conventionally known method can be used. Specifically, for example, the pressure-sensitive adhesive tape can be produced by adding the (meth)acrylic copolymer, Component A, etc. to a solvent, and then thoroughly stirring the mixture to obtain a pressure-sensitive adhesive solution, which is then coated on the release layer of the separator and dried to form a pressure-sensitive adhesive layer.

[0073] The applications of the pressure-sensitive adhesive tape of the present disclosure are not particularly limited, and it can be used for, for example, assembling portable electronic devices such as mobile phones and personal digital assistants (PDAs), and for manufacturing devices that emit or receive electromagnetic waves to fix automotive electronic components such as automotive panels to the vehicle body. In particular, the pressure-sensitive adhesive tape of the present disclosure has excellent adhesive strength to silicone-based adherends, and is therefore preferably used for bonding silicone-based adherends. Examples of the silicone-based adherends include silicone rubber, silicone foam, and objects with silicone coatings, and specific examples include electronic component parts, vehicle components, construction components, and medical components.

[0074] Examples of electronic device components include heat-dissipating pads and sheets, adhesives and sealants for securing electrical and electronic components, potting agents and coating agents for protecting electrical and electronic components, semiconductor die-bonding materials, potting materials for sealing electronic circuits, rolls for office automation equipment, anode caps, glass sleeve consolidation materials for cables, polymer insulators, and electrically insulating resin varnishes. Examples of vehicle components include heat-dissipating pads and sheets, heat-dissipating foam, heat-resistant foam, heat-resistant hoses, O-rings, adhesives and sealants for securing vehicle components, and potting agents and coating agents for protecting vehicle equipment. Examples of building components include building gaskets and vibration-isolating agents, insulating rubber, heat-dissipating rubber, insulating foam, heat-dissipating foam, adhesives and sealants for securing building components, and potting agents and coating agents for protecting building equipment. Examples of medical components include catheters and tubes, sealing materials and gaskets for medical devices, and adhesives and sealants for securing medical components.

[0075] The present disclosure also provides a laminate comprising a structure in which the pressure-sensitive adhesive tape of the present disclosure is attached to a silicone-based adherend. The laminate of the present disclosure has a low content of organic fluorine resin and is therefore environmentally friendly.

[0076] The laminate of the present disclosure is not particularly limited as long as it has a structure in which the pressure-sensitive adhesive tape is attached to a silicone-based adherend, but examples include a laminate in which a member 2 containing a silicone-based resin and another member 3 are attached using the pressure-sensitive adhesive tape 1, as shown in Figure 1. Other examples include laminates in which members containing silicone-based resins are attached to each other. Specific examples include structures in which the pressure-sensitive adhesive tape is attached to silicone-based adherends such as heat-dissipating pads and sheets, adhesives and sealants for fixing electrical and electronic components, potting agents and coating agents for protecting electrical and electronic components, semiconductor die-bonding materials, electronic circuit sealing potting materials, rolls for office automation equipment, anode caps, glass sleeve bundling materials for cables, polymer insulators, and electrically insulating resin varnishes, as well as the above-mentioned vehicle parts, construction parts, and medical parts.

[0077] The present disclosure also relates to an electronic device including the pressure-sensitive adhesive tape of the present disclosure. The electronic device of the present disclosure has a low content of organic fluorine resin and is therefore environmentally friendly.

[0078] The electronic device of the present disclosure is not particularly limited as long as it is an electronic device that includes the pressure-sensitive adhesive tape, and examples thereof include electronic devices that have as a component the above-mentioned laminate shown in Fig. 1 , and electronic devices that have as a component a laminate formed by bonding together members that contain a silicone-based resin. Specific examples thereof include mobile phones, smartphones, tablets, personal computers (PCs), notebook computers, game consoles, display terminals, electronic paper terminals, wristwatches and wristwatch-type electronic devices, eyeglass-type electronic devices, and goggle-type electronic devices, which include the structures exemplified above as the laminate of the present disclosure.

[0079] According to the present disclosure, it is possible to provide a pressure-sensitive adhesive tape that can exhibit excellent adhesive strength to a silicone-based adherend without using a silicone-based pressure-sensitive adhesive and without prior surface treatment of the adherend. Furthermore, according to the present disclosure, it is possible to provide a laminate having a structure to which the pressure-sensitive adhesive tape is attached. Furthermore, according to the present disclosure, it is possible to provide an electronic device including the pressure-sensitive adhesive tape.

[0080] 1 is a cross-sectional view schematically illustrating an example of a laminate according to the present disclosure. 2 is a schematic diagram illustrating a method for a high-temperature retention test.

[0081] The following examples further illustrate aspects of the present disclosure, but the present disclosure is not limited to these examples.

[0082] (Synthesis of (meth)acrylic copolymers a-k) Ethyl acetate was added as a solvent to a reactor equipped with a thermometer, a stirrer, and a condenser, and the atmosphere was replaced with nitrogen. The reactor was then heated to initiate reflux. After the solvent boiled, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10 times with ethyl acetate was added as a polymerization initiator. An ethyl acetate solution of a monomer mixture having the content (% by mass) shown in Table 1 was then added dropwise from the dropping funnel to the reactor over 2 hours so that the monomer concentration became 45% by mass. After the completion of the dropwise addition, a polymerization reaction was carried out for 4 hours to obtain ethyl acetate solutions of (meth)acrylic copolymers a-k. The resulting ethyl acetate solutions of acrylic copolymers a-g were filtered, and the resulting filtrate was supplied to a gel permeation chromatograph (Waters, 2690 Separations Module). GPC measurement was performed at a sample flow rate of 1 mL / min and a column temperature of 40°C to measure the polystyrene-equivalent molecular weight of the acrylic copolymer and determine the weight-average molecular weight (Mw). The column used was a GPC KF-806L (manufactured by Showa Denko KK), and the detector was a differential refractometer. The results are shown in Table 1.

[0083] (Synthesis of (meth)acrylic copolymer l) Ethyl acetate was added as a solvent to a reactor equipped with a thermometer, a stirrer, and a cooling tube, and the inside was replaced with nitrogen. The reactor was then heated to initiate reflux. A polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added to the reactor, and then 96.6 parts by mass of n-heptyl acrylate, 2.9 parts by mass of acrylic acid, and 0.5 parts by mass of 2-hydroxyethyl acrylate were added dropwise over 2 hours. After completion of the dropwise addition, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added again to the reactor, and a polymerization reaction was carried out for 4 hours to obtain an ethyl acetate solution of acrylic copolymer l. The resulting ethyl acetate solution of acrylic copolymer l was filtered through a filter, and the resulting filtrate was supplied to a gel permeation chromatograph (Waters, 2690 Separations Module). GPC measurement was performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C, and the polystyrene-equivalent molecular weight of the acrylic copolymer was measured to determine the weight average molecular weight (Mw). A GPC KF-806L (Showa Denko KK) was used as the column, and a differential refractometer was used as the detector. The results are shown in Table 1.

[0084] The structural unit monomers of the (meth)acrylic copolymer shown in Table 1 are as follows: EA: ethyl acrylate, BA: n-butyl acrylate, HPA: n-heptyl acrylate, 2OA: 2-octyl acrylate, 2EHA: 2-ethylhexyl acrylate, HEA: 2-hydroxyethyl acrylate, DMAA: N,N-dimethylacrylamide, AAc: acrylic acid

[0085]

[0086] Example 1 (1) Preparation of Adhesive Tape To the resulting ethyl acetate solution of (meth)acrylic copolymer a, 3.0 parts by mass of KBM-602 (manufactured by Shin-Etsu Chemical Co., Ltd.) was added as an aliphatic amine-based silane coupling agent per 100 parts by mass of the solid content of (meth)acrylic copolymer a. Ethyl acetate was then added to the resulting mixture to a solid content of 30%, and the mixture was thoroughly mixed to prepare an adhesive solution. The prepared adhesive solution was applied to the release layer of a 75 μm thick separator (manufactured by Toyo Cross Co., Ltd., "SP3000") and dried at 110°C for 3 minutes to form a 50 μm thick adhesive layer. Another 25 μm thick separator (manufactured by Toyo Cross Co., Ltd., "SP8001") was then prepared, and the release layer was placed opposite the formed adhesive layer. This was then aged at 40°C for 48 hours to obtain an adhesive tape. Note that the separator used here does not contain a fluorine component such as PFAS.

[0087] (2) Measurement of gel fraction of adhesive layer The adhesive of the adhesive layer was ０ (g) was scraped off, immersed in 50 mL of ethyl acetate, and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the ethyl acetate and the adhesive that had absorbed the ethyl acetate and swollen were separated using a metal mesh (opening #200 mesh), and the separated adhesive was dried at 110°C for 1 hour. The mass of the adhesive including the metal mesh after drying was measured, and the gel fraction was calculated using the above formula (1). The results are shown in Table 2.

[0088] (3) Measurement of the relative intensity of the negative ion peak in the m / z 26 region after peeling off the adhesive tape. The surface of a 50 mm x 125 mm SUS304 plate was washed with ethanol and then wiped dry. A film adhesive tape (manufactured by Teraoka Seisakusho, "767") having a silicone-based adhesive layer on one side was cut to a size of 30 mm wide and 70 mm long. The separator on the adhesive layer side that was not the silicone-based adhesive layer was then peeled off, and the adhesive layer was attached to the SUS304 plate. The separator on the silicone-based adhesive layer side was then peeled off to expose the silicone-based adhesive layer. A 1 mm-thick silicone rubber (manufactured by Togawa Rubber Co., Ltd., K-125(50)) cut to a size of 30 mm wide and 70 mm long was attached to the silicone-based adhesive layer to prepare a silicone-based adherend. The adhesive tape obtained in the above-described "(1) Preparation of Adhesive Tape" was cut to a size of 25 mm wide and 70 mm long. The separator on one side of the cut adhesive tape was peeled off, and one side of the adhesive tape was backed with the corona-treated surface of a 23 μm thick polyethylene terephthalate (PET) film. The separator on the other side of the backed adhesive tape was peeled off, and the tape was attached to the silicone rubber surface of the silicone-based adherend. A 2 kg roller was then reciprocated once at a speed of 300 mm / min to press the tape together, and the tape was left to stand in an atmosphere of 23°C and 50% RH for 72 hours to produce a laminate. A peel test was performed on the produced laminate in accordance with JIS Z0237 using a tensile tester (Shimadzu Corporation, "AG-IS") at 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°. The adhesive tape was then peeled from the silicone-based adherend. After the peeling test, the silicone rubber peeled from the adhesive tape was manually peeled at a speed of approximately 300 mm / min and a peeling angle of approximately 90°, to peel the silicone rubber from the film adhesive tape having a silicone adhesive layer. After peeling from the silicone-based adherend, the peeled silicone rubber was cut into approximately 1 cm square pieces using a cutter or scissors to prepare a measurement sample. The surface of the measurement sample that had been in contact with the adhesive tape was placed on the surface of the ethyl acetate solution in an aluminum cup with an inner diameter of 5 cm and containing 2 mL of ethyl acetate, and then washed with ethyl acetate by shaking back and forth at 1 cm intervals 80 times per minute (i).Furthermore, another aluminum cup with an inner diameter of 5 cm containing 2 mL of ethyl acetate was prepared, and after similar cleaning, the measurement sample was heated in an oven at normal pressure at 80°C for 10 minutes (ii). The above operations (i) and (ii) constituted one set, and a total of four sets were performed, resulting in a total of eight cleanings with ethyl acetate. Note that a new aluminum cup and ethyl acetate were used for each of operations (i) and (ii). TOF-SIMS measurement was performed on the surface cleaned with ethyl acetate, and the obtained spectral data was analyzed using analysis software ("SurfaceLab 7" manufactured by ION-TOF Corporation) to obtain the relative intensity of the negative ion peak in the m / z region of 26 after peeling off the adhesive tape. The results are shown in Table 1. Specifically, the TOF-SIMS measurement was performed as follows. (TOF-SIMS Measurement) TOF-SIMS measurement was performed using a time-of-flight secondary ion mass spectrometer (manufactured by ION-TOF, "TOF.SIMS5"), and the measurement conditions were as described below. From the obtained secondary ion spectrum, the sum (area) of the peaks of negative ions in the m / z 26 region was divided by the sum (area) of the peaks of all negative ions to calculate the value. <Measurement conditions for TOF-SIMS measurement> Primary ion species: Bi3++ Acceleration voltage: 25 kV Detected ion polarity: negative (negative ion) Measurement range: 500 μm × 500 μm Number of pixels: 128 × 128 (pixels) Number of scans: 25 scans Mass range (m / z): 0 to 850.

[0089] (Examples 2 to 27, Comparative Examples 1 to 4, 6 to 9) Pressure-sensitive adhesive tapes were produced in the same manner as in Example 1, except that the composition of the pressure-sensitive adhesive layer was changed as shown in Tables 2 to 5 and 9. The resulting pressure-sensitive adhesive tapes were then irradiated with electron beams using an electron beam irradiation device (manufactured by NHV Corporation, "EBC-200") under the electron beam irradiation conditions shown in Tables 2 to 5 and 9, thereby crosslinking the pressure-sensitive adhesive components and forming pressure-sensitive adhesive layers, thereby obtaining pressure-sensitive adhesive tapes. Electron beams were irradiated from both sides of the pressure-sensitive adhesive tape, with half of the total dose applied. The gel fraction of the pressure-sensitive adhesive layer was measured in the same manner as in Example 1. The results are shown in Tables 2 to 5 and 9.

[0090] (Examples 28-29) Pressure-sensitive adhesive tapes were prepared in the same manner as in Example 1, except that the composition of the pressure-sensitive adhesive layer was changed as shown in Table 5, and benzophenone was added to the pressure-sensitive adhesive layer as a radical generator for UV crosslinking in the amount shown in Table 5. The resulting pressure-sensitive adhesive tape was then irradiated with UV light containing light having a wavelength of 365 nm using a chemical lamp (Toshiba Corporation, "FL20S-BL") under the UV irradiation conditions shown in Table 5, thereby crosslinking the pressure-sensitive adhesive component and forming a pressure-sensitive adhesive layer, thereby obtaining a pressure-sensitive adhesive tape. UV irradiation was performed from both sides of the pressure-sensitive adhesive tape, with half of the integrated light amount applied. The gel fraction of the pressure-sensitive adhesive layer was measured in the same manner as in Example 1. The results are shown in Table 5.

[0091] Comparative Example 5 100 parts by mass of a styrene-ethylene-butylene-styrene (SEBS) triblock copolymer (DYNARON 8300, manufactured by ENEOS Materials Corporation) and 30 parts by weight of a tackifier resin (ALCON P-125, manufactured by Arakawa Chemical Industries, Ltd.) were dissolved in toluene to prepare a pressure-sensitive adhesive solution with a solids content of 30%, and a pressure-sensitive adhesive tape was produced in the same manner as in Example 1, except that this pressure-sensitive adhesive solution was used. Measurement of the gel fraction of the pressure-sensitive adhesive layer was carried out in the same manner as in Example 1, except that ethyl acetate was changed to toluene. The results are shown in Table 9.

[0092] (Example 30) (1) Preparation of Pressure-Sensitive Adhesive Tape First, a pressure-sensitive adhesive solution (a) for forming the pressure-sensitive adhesive layer (A) and a pressure-sensitive adhesive solution (b) for forming the pressure-sensitive adhesive layer (B), in which an isocyanate crosslinking agent (Desmodur L75, manufactured by Covestro) was added at 0.2 parts by mass (solid content ratio) per 100 parts by mass of the (meth)acrylic copolymer, were prepared in the same manner as in Example 1, except that the composition of the pressure-sensitive adhesive layer was changed as shown in Tables 6 to 8. Next, the prepared pressure-sensitive adhesive solution (a) was applied to the release layer of a 75 μm-thick separator ("SP3000", manufactured by Toyo Cross Co., Ltd.), and then dried at 110° C. for 3 minutes to form a pressure-sensitive adhesive layer. A laminate was prepared by superposing a pressure-sensitive adhesive layer formed on one side of a 23 μm-thick PET film (manufactured by Futamura Chemical Co., Ltd., "FE2002-23"). The prepared laminate was irradiated with an electron beam using an electron beam irradiation device (manufactured by NHV Corporation, "EBC-200") to crosslink the pressure-sensitive adhesive component, thereby forming a pressure-sensitive adhesive layer (A) with a thickness of 75 μm. The electron beam was irradiated from both sides of the laminate, with half of the total dose. Furthermore, the prepared pressure-sensitive adhesive solution (b) was applied to the release layer of the separator (B) listed in Table 6, and then dried at 110°C for 3 minutes to form a pressure-sensitive adhesive layer (B) with a thickness of 42 μm. Then, the pressure-sensitive adhesive layer (B) was superposed on the side of the substrate not having the pressure-sensitive adhesive layer (A) of the laminate on which the pressure-sensitive adhesive layer (A) was formed, thereby forming an integrated laminate, and then aging was performed in an environment of 40°C for 48 hours. Then, the separator on the pressure-sensitive adhesive layer (A) side was peeled off, and a separator (A) shown in Table 6 was laminated thereon. The pressure-sensitive adhesive tape with the replaced separator was placed in an oven set to 60°C and 50% RH, and allowed to stand for 168 hours under conditions of 60°C and 50% RH, thereby obtaining a pressure-sensitive adhesive tape having a substrate and a pressure-sensitive adhesive layer and a separator on both sides of the substrate.

[0093] (2) Measurement of Gel Fraction of Pressure-Sensitive Adhesive Layer First, the laminate on which the pressure-sensitive adhesive layer (A) was formed in the above-described "(1) Preparation of Pressure-Sensitive Adhesive Tape" was cut into a size of 25 mm wide and 60 mm long, and then the separator (A) was peeled off from the cut laminate to prepare a test piece for gel fraction measurement. Next, the prepared test piece for gel fraction measurement was immersed in 50 mL of ethyl acetate and shaken in a shaker at 23 ° C and 200 rpm for 24 hours. After that, the ethyl acetate and the test piece that had absorbed and swollen the ethyl acetate were separated using a metal mesh (opening #200 mesh). The separated test piece was then dried at 110 ° C for 1 hour. The mass of the test piece including the dried metal mesh was measured, and the gel fraction (% by mass) was calculated using the above formula (2). The results are shown in Table 6.

[0094] (3) Measurement of the relative intensity of the negative ion peak in the m / z 26 region after peeling off the adhesive tape The relative intensity of the negative ion peak in the m / z 26 region after peeling off the adhesive tape was measured in the same manner as in Example 1, except that the adhesive layer (B) was backed by the corona-treated surface of a 23 μm-thick polyethylene terephthalate (PET) film and the adhesive layer (A) was attached to the silicone rubber surface of the silicone-based adherend. The results are shown in Table 6.

[0095] (4) Measurement of Relative Intensity in XPS Measurement of Separator After Exposure to High Temperature and High Humidity Environment First, the separator (B) in the obtained pressure-sensitive adhesive tape was peeled from the pressure-sensitive adhesive layer (B), and then a 2 kg rubber roller was used to roll back and forth once at a speed of 300 mm / min to press the pressure-sensitive adhesive layer (B) onto the corona-treated surface of a 23 μm-thick polyethylene terephthalate (PET) film to prepare a backing test piece. The prepared test piece was then placed in a constant temperature and humidity oven set at 60° C. and 50% RH, and allowed to stand under the conditions of 60° C. and 50% RH for 168 hours. After that, the test piece was removed from the constant temperature and humidity oven and air-cooled in an environment of 23° C. for 30 minutes. Furthermore, the separator (A) was peeled from the pressure-sensitive adhesive layer (A) using a tensile tester (Shimadzu Corporation, "AG-IS") in accordance with JIS Z0237 under conditions of 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°. Then, narrow scan analysis of C1s, O1s, and Si2p in XPS measurement was performed on the peel interface between the separator (A) and the pressure-sensitive adhesive layer (A) in the separator (A) peeled from the pressure-sensitive adhesive layer (A) under the following conditions. After calibrating the C1s peak top at 284.8 eV, the relative intensity of the peak at 103.9 eV was calculated, with the maximum value set to 1 and the minimum value set to 0 within the Si2p measurement range, thereby obtaining the relative intensity in the XPS measurement of the separator. The results are shown in Table 6. <XPS measurement conditions> Measurement device: PHI5000VersaProbeII (manufactured by ULVAC-PHI) X-ray source: Al Kα ray (1486.6 eV) Photoelectron take-off angle: 45 degrees Pass energy: 23.5 eV (Si2p), 58.7 eV (C1s, O1s) Measurement setting range: 94.0 eV to 114.0 eV (Si2p), 278.0 eV to 298.0 eV (C1s), 298.0 eV to 523.0 eV (O1s) Step width: 0.1 eV (Si2p), 0.125 eV (C1s, O1s) Number of sweeps: 3 (Si2p), 2 (C1s), 1 (O1s) Number of cycles: 10

[0096] (Examples 31 to 34, 38 to 44) Pressure-sensitive adhesive tapes were prepared and various measurements were carried out in the same manner as in Example 30, except that in the above-mentioned "(1) Preparation of pressure-sensitive adhesive tapes", the types of separator (A), substrate, and separator (B), and the compositions and thicknesses of the pressure-sensitive adhesive layer (A) and pressure-sensitive adhesive layer (B) were changed as shown in Tables 6 to 8. The results are shown in Tables 6 to 8.

[0097] (Examples 35 to 37, 45 to 46) Pressure-sensitive adhesive tapes were prepared and various measurements were carried out in the same manner as in Example 30, except that in the above-mentioned "(1) Preparation of pressure-sensitive adhesive tapes", the types of separator (A), substrate, and separator (B), and the compositions and thicknesses of the pressure-sensitive adhesive layer (A) and pressure-sensitive adhesive layer (B) were as shown in Tables 6 to 8, and after laminating a separator (A) shown in Tables 6 to 8, the pressure-sensitive adhesive tape with the separator replaced was placed in an oven set to 23°C and 50% RH and left to stand for 168 hours under conditions of 23°C and 50% RH. The results are shown in Tables 6 to 8.

[0098] (Example 47) In the above-mentioned "(1) Preparation of pressure-sensitive adhesive tape", the types of separator (A), substrate, and separator (B), and the compositions and thicknesses of pressure-sensitive adhesive layer (A) and pressure-sensitive adhesive layer (B) were changed as shown in Table 8, and further, the pressure-sensitive adhesive layer (A) was formed without electron beam irradiation, except that pressure-sensitive adhesive tapes were prepared in the same manner as in Example 30, and various measurements were carried out. The results are shown in Table 8.

[0099] The types of separators shown in Tables 6 to 8 are as follows: Separator A: SP8001 (manufactured by Toyo Cross Co., Ltd.) Separator B: SP3030 (manufactured by Toyo Cross Co., Ltd.) Separator C: RF2 PET50cs14EX (manufactured by Aim Co., Ltd.) Separator D: Cerapeel MDA (manufactured by Toray Industries, Inc.) Separator E: MRQ75 (manufactured by Mitsubishi Chemical Corporation) Separator F: SP3000 (manufactured by Toyo Cross Co., Ltd.) Separator G: SP1007 (manufactured by Toyo Cross Co., Ltd.) Separator H: SP4020 (manufactured by Toyo Cross Co., Ltd.) Separator I: SP4030 (manufactured by Toyo Cross Co., Ltd.) Separator J: MRV75 (V06) (manufactured by Mitsubishi Chemical Corporation) Separator K: MRV100 (VOC) (manufactured by Mitsubishi Chemical Corporation) It should be noted that none of the separators shown in Tables 6 to 8 contain a fluorine component such as PFAS.

[0100] <Evaluation> The pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 2 to 9.

[0101] (Adhesion strength to silicone-based adherend) The surface of a 50 mm x 125 mm SUS304 plate was washed with ethanol and then wiped dry. A film adhesive tape (manufactured by Teraoka Seisakusho Co., Ltd., "767") having a silicone-based adhesive layer on one side was cut to a size of 30 mm wide and 70 mm long. The separator on the adhesive layer side that was not the silicone-based adhesive layer was then peeled off, and the adhesive layer (the adhesive layer that was not the silicone-based adhesive layer) was attached to the SUS304 plate. The separator on the silicone-based adhesive layer side was then peeled off to expose the silicone-based adhesive layer. A 1 mm-thick silicone rubber (manufactured by Togawa Rubber Co., Ltd., K-125(50)) cut to a size of 30 mm wide and 70 mm long was attached to the silicone-based adhesive layer to prepare a silicone-based adherend. The obtained pressure-sensitive adhesive tape was cut to a size of 25 mm wide and 70 mm long, the separator (separator (B) in Examples 30 to 47) on one side of the cut pressure-sensitive adhesive tape was peeled off, and one side of the pressure-sensitive adhesive tape was adhered to the corona-treated surface of a 23 μm-thick polyethylene terephthalate (PET) film to form a backing. The separator (separator (A) in Examples 30 to 47) on the other side of the backing pressure-sensitive adhesive tape was peeled off, and the tape was adhered to the silicone rubber surface of the silicone-based adherend, followed by pressure bonding using a 2 kg roller moving back and forth at a speed of 300 mm / min, and then allowed to stand for 72 hours in an atmosphere of 23°C and 50% RH to prepare a measurement sample. The prepared measurement samples were peeled from the silicone-based adherend using a tensile tester (Shimadzu Corporation, "AG-IS") in accordance with JIS Z0237 under conditions of 23°C, a pulling speed of 300 mm / min, and a peel angle of 180°, and the 180° peel strength (N / 25 mm) was measured. Using the obtained 180° peel strength, the adhesive strength of the pressure-sensitive adhesive tape to the silicone-based adherend was evaluated according to the following criteria: ⊚: The 180° peel strength was 3.0 N / 25 mm or more. ◯: The 180° peel strength was 2.0 N / 25 mm or more but less than 3.0 N / 25 mm. ×: The 180° peel strength was less than 2.0 N / 25 mm.For Comparative Example 4, the pressure-sensitive adhesive tape could not be attached to a silicone-based adherend, and therefore the 180° peel force could not be measured. Therefore, the 180° peel force (N / 25 mm) against silicone rubber in Table 5 is recorded as "-".

[0102] (High-Temperature Holding Power) Figure 2 shows a schematic diagram of the high-temperature holding power test method. First, in accordance with JIS Z-1528, the obtained pressure-sensitive adhesive tape was cut into a width of 25 mm and a length of 60 mm to prepare a test piece 5. After peeling off the separator (separator (B) for Examples 30 to 47) on one side of the test piece 5, the exposed pressure-sensitive adhesive layer (pressure-sensitive adhesive layer (B) for Examples 30 to 47) was backed with a polyethylene terephthalate (PET) film 4. After peeling off the separator (separator (A) for Examples 30 to 47) on the other surface of test piece 5, the exposed pressure-sensitive adhesive layer (pressure-sensitive adhesive layer (A) for Examples 30 to 47) was attached to a cold-rolled stainless steel plate 6 (SUS304 plate cleaned with ethanol and wiped dry) 2.0 mm thick, 50 mm wide, and 75 mm long at 23°C so that the length was 25 mm. The test piece 5 was attached to the SUS304 plate 6 while being shifted in the longitudinal direction so that it protruded from the end of the SUS304 plate 6, and then pressed with a 2 kg roller moving back and forth once to prepare a measurement sample. The measurement sample was left to stand for 20 minutes in an atmosphere of 23°C and 50% RH, and then a 1 kg weight 7 was attached to the measurement sample in an 80°C environment so that a load was applied to the measurement sample in the shear direction. The time when weight 7 was attached was designated as the starting time (0 hour), and a high-temperature retention test was performed in which the load applied by weight 7 was maintained for 1 hour. The test piece 5 was checked for falling, and if it had not fallen after 1 hour, the amount of movement (deviation) from the position at the start time was measured with a scale magnifier. The high-temperature holding power of the pressure-sensitive adhesive tape was evaluated according to the following criteria: Excellent: The test piece was displaced 0.1 mm or less. Good: The test piece was displaced more than 0.1 mm and 0.5 mm or less. Fair: The test piece was displaced more than 0.5 mm and did not fall. Bad: The test piece fell during the high-temperature holding power test. Note that even if the evaluation is "Bad", the pressure-sensitive adhesive tape of the present disclosure can be used without any problems depending on the application.

[0103] (Coatability) In the above-mentioned "(1) Production of Pressure-Sensitive Adhesive Tape," starting from the step of coating the obtained pressure-sensitive adhesive solution onto a separator (for Examples 30 to 47, the step of coating the separator (A) with the pressure-sensitive adhesive solution that forms the pressure-sensitive adhesive layer (A)), coatability was evaluated according to the following criteria. ○: Coating was possible without any problems. △: Coating was possible, but cloudiness or streaks or the like occurred in the coated layer. ×: Coating was not possible.

[0104] (Separator Peelability) For Examples 30 to 47 in Tables 6 to 8, the resulting pressure-sensitive adhesive tapes were cut to a size of 25 mm wide and 70 mm long. The separator (B) was peeled from the cut pressure-sensitive adhesive tape, and the exposed pressure-sensitive adhesive surface was attached to a 50 mm x 125 mm SUS304 plate whose surface had been washed with ethanol and then wiped dry. The plate was then left to stand for 72 hours in an atmosphere of 23°C and 50% RH to prepare a measurement sample. For the prepared measurement sample, the separator (A) was peeled from the pressure-sensitive adhesive tape in accordance with JIS Z0237 using a tensile tester (manufactured by Shimadzu Corporation, "AG-IS") under conditions of 23°C, a tensile speed of 300 mm / min, and a peel angle of 180°, and the 180° peel strength (N / 25 mm) was measured. The obtained 180° peel strength was used to evaluate the separator peelability of the pressure-sensitive adhesive tape according to the following criteria. ⊚: The 180° peel strength was 0.50 N / 25 mm or less. ◯: The 180° peel strength was greater than 0.50 N / 25 mm and less than 1.00 N / 25 mm. ×: The 180° peel strength was greater than 1.00 N / 25 mm. Even if the evaluation is "×", the pressure-sensitive adhesive tape of the present disclosure can be used without any problems depending on the application.

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112]

[0113] According to the present disclosure, it is possible to provide a pressure-sensitive adhesive tape that can exhibit excellent adhesive strength to a silicone-based adherend without using a silicone-based pressure-sensitive adhesive and without prior surface treatment of the adherend. Furthermore, according to the present disclosure, it is possible to provide a laminate having a structure to which the pressure-sensitive adhesive tape is attached. Furthermore, according to the present disclosure, it is possible to provide an electronic device including the pressure-sensitive adhesive tape.

[0114] DESCRIPTION OF SYMBOLS 1 Adhesive tape 2 Member containing silicone resin 3 Other member 4 Polyethylene terephthalate (PET) film 5 Test piece 6 SUS304 plate 7 Weight (1 kg)

Claims

1. An adhesive tape having an adhesive layer containing a (meth)acrylic copolymer, a laminate obtained by laminating the pressure-sensitive adhesive tape to silicone rubber fixed to a SUS304 plate is left to stand for 72 hours in an environment of 23°C and 50% RH, and then a peel test is performed using a tensile tester under conditions of 23°C, 50% RH and a peel rate of 300 mm / min, in which the pressure-sensitive adhesive tape in the laminate is peeled off from the silicone rubber at an angle of 180°; after the peel test, the surface of the silicone rubber from which the pressure-sensitive adhesive tape has been peeled off is washed at least eight times with ethyl acetate, and then TOF-SIMS measurement is performed on the washed surface, and the peak intensity of negative ions in the m / z 26 region relative to the peak intensity (total) of all negative ions (26 / total) is 2.50×10 −3 or more; Used to bond silicone-based adherends An adhesive tape characterized by:

2. The adhesive layer contains component A including at least one selected from a silane coupling agent having an aliphatic amino group, a silane coupling agent having a skeleton in which the aliphatic amino group is protected, a compound having a structure derived from a silane coupling agent having an aliphatic amino group, and a compound having a structure derived from a silane coupling agent having a skeleton in which the aliphatic amino group is protected; The content of the component A relative to 100 parts by mass of the (meth)acrylic copolymer is 8.0 parts by mass or less. The adhesive tape according to claim 1.

3. An adhesive tape as described in claim 2, wherein the content of component A per 100 parts by mass of the (meth)acrylic copolymer is 1.5 parts by mass or more.

4. An adhesive tape as described in claim 3, wherein the content of component A per 100 parts by mass of the (meth)acrylic copolymer is greater than 3.0 parts by mass.

5. An adhesive tape according to claim 2, 3 or 4, wherein at least one of the aliphatic amino groups in component A is a primary aliphatic amino group or a secondary aliphatic amino group having a non-cyclic structure.

6. The (meth)acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester, The structural units derived from (meth)acrylic acid alkyl esters do not have structural units derived from (meth)acrylic acid alkyl esters having an ester terminal alkyl group with 2 or less carbon atoms, or the structural units derived from (meth)acrylic acid alkyl esters have structural units derived from (meth)acrylic acid alkyl esters having an ester terminal alkyl group with 2 or less carbon atoms, and the content of the structural units derived from (meth)acrylic acid alkyl esters having an ester terminal alkyl group with 2 or less carbon atoms is 25 mass% or less.

5. The adhesive tape according to claim 1, wherein

7. The structural unit derived from a (meth)acrylic acid alkyl ester has a structural unit derived from a (meth)acrylic acid alkyl ester, 5. The adhesive tape according to claim 1, which comprises a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl group at the ester terminal having 7 carbon atoms.

8. An adhesive tape as described in claim 1, 2, 3 or 4, wherein the (meth)acrylic copolymer does not have any constituent units derived from a carboxy group-containing monomer.

9. An adhesive tape according to claim 1, 2, 3 or 4, wherein the adhesive layer contains a component that crosslinks upon irradiation with an electron beam or ultraviolet light.

10. An adhesive tape as described in claim 1, 2, 3 or 4, wherein the adhesive layer contains a radical generator.

11. An adhesive tape according to claim 1, 2, 3 or 4, wherein the adhesive layer has a gel fraction of 35 mass% or more.

12. The pressure-sensitive adhesive layer contains a component that crosslinks upon electron beam irradiation or ultraviolet light irradiation, The pressure-sensitive adhesive layer has a gel fraction of 35% by mass or more. The adhesive tape according to claim 1, 2, 3 or 4.

13. Further comprising a separator, 5. The adhesive tape according to claim 1, wherein the release layer of the separator does not contain an organic fluorine compound.

14. Further comprising a separator, 5. The pressure-sensitive adhesive tape according to claim 1, wherein when the separator is peeled at an angle of 180° from the pressure-sensitive adhesive layer in an environment of 23°C and 50% RH and the surface of the peel interface between the separator and the pressure-sensitive adhesive layer is measured by XPS, the relative intensity of the peak at 103.9 eV is 0.170 or less.

15. 5. The pressure-sensitive adhesive tape according to claim 1, wherein the silicone-based adherend is an electronic device part, a vehicle part, a construction part, or a medical part.

16. A laminate comprising a structure in which the pressure-sensitive adhesive tape according to claim 1, 2, 3 or 4 is attached to a silicone-based adherend.

17. An electronic device comprising the adhesive tape according to claim 1 , 2 , 3 or 4 .